Thrombectomy is a procedure for removing thrombus from the vasculature. Mechanical and fluid based systems are used to remove thrombus and accordingly open clogged or partially clogged vessels. With fluid based systems an infusion fluid including one or more of saline, lytics and the like is infused to a treatment area of a vessel with a catheter, for instance a thrombectomy catheter. The hydrodynamic force of the infusion fluid and optionally the characteristics of the lytics dislodge thrombus and accordingly open the vessel.
In one example, the infusion fluid is delivered to the thrombectomy catheter in a pulsed manner with a pump including a single piston. The piston is moved in a first direction to draw fluid into a cylinder, and then moved in a second direction to push the fluid out of the cylinder to a treatment feature of the thrombectomy catheter (e.g., an orifice). The pulses of fluid generated by the piston pump are then discontinuously applied through the treatment feature of the thrombectomy catheter to dislodge thrombus from the vessel wall. Optionally, the cylinder is prefilled with a fluid (e.g., contrast fluid or infusion fluid for thrombectomy) and the piston is driven in a single direction to gradually infuse the fluid. Upon full delivery of the fluid the cylinder must be refilled before operation is continued.
One example of an injection system and a pump system therein are described in U.S. Pat. No. 5,916,197. In the example pump system at least one chamber has disposed therein a pressurizing mechanism to pressurize liquid medium within the chamber. Preferably, the pressurizing mechanism positively displaces the liquid medium through generally linear motion of the pressurizing mechanism. Through reciprocating linear motion of the pressurizing mechanism (for example, a piston), the liquid medium is alternatively drawn into the chamber from a source of liquid medium (for example, a container) and forced out of the chamber under a desired pressure.
Another example of a system for delivery of a medical fluid is described in US Published Patent Application 2011/0152681. The system includes a pump system including a pressurizing unit to pressurize the medical fluid and a drive system in operative connection with the pressurizing unit. The pump system exhibits variation in pressure during operation. The system further includes a compensating system in fluid connection with the medical fluid pressurized by the pressurizing unit. The compensating system defines a displacement volume in fluid connection with the pressurized medical fluid that is altered in a predetermined manner to alter the variation in pressure. The compensating system can, for example, reduce pulsatility of pressure during flow.
Yet another example of a system for delivery of a medical fluid is described in US Published Patent Application 2012/0244018. The system includes a pump including a plurality of at least three chambers. Each of the plurality of chambers includes an inlet through which fluid is drawn into the chamber and an outlet from which fluid is expelled from the chamber. The pump system further includes a common outlet channel fluid communication with the outlet of each of the plurality of chambers and a plurality of at least three pistons. Each of the positions is slidably disposed within a respective one of the plurality of chambers. The system further includes a drive system including a cam shaft including a plurality of at least three cam lobes. The drive system further includes a plurality of at least three cam lobe followers. Each of the cam lobe followers is in operative connective with a respective one of the plurality of cam lobes and is adapted to be placed in operative connection with a respective one of the plurality of pistons. The profile of each of the plurality of cam lobes is adapted to provide a transient increase or spike in calculated theoretical output of the pump system to reduce periodic variation in measured output thereof.
In other examples, a pump with a reciprocating piston includes a drive mechanism, such as a motor, that reverses its direction to accordingly reverse the movement of the piston. The piston is accordingly decelerated and accelerated as the piston transitions from its stroke in a first direction to a second stroke in an opposed direction.
In another example a multi-cylinder pump including a plurality of corresponding pistons are coordinated to provide a continuous flow of infusion fluid. Stated another way, the plurality of pistons are operated out of sync with one another to ensure that as one of the cylinders is filling with infusion fluid another of the cylinders is providing infusion fluid output. A mechanism (e.g., a software algorithm, mechanical mechanism or the like) is used to coordinate the pistons in this manner